"Context" affects perception, as proved by the Gestalt. Context includes our ideas of our environment.
Regexes (short for Regular Expressions) are not generally considered high-level pattern recognition systems in computer science, as they are generally expressed in a single, simple (regular), string. You can find more information about them by checking out the documentation of the Python or Perl programming languages. Generalised pattern-recognition systems are considerably more involved, and often lack the ability to perform "associations" (call-outs) as they are interpreting their environment.
Solso, R., Cognition and the Visual Arts, Bradford, Cambridge, 1994.
Recognising Known Patterns within a Field
Identification and Association
Auxiliary Elements for document tb.percept.trident.throw.htm
Part of Toolboxes and Treasure-chests.